The current study aims to assess the kinetics of population growth of Rhodotorula oryzicola and the production of β-1,3-glucanase (EC 3.2.1.39) enzyme by this yeast. It also aims to obtain the optimum conditions of β-1,3-glucanase enzymatic activity by varying the pH as well as to study the enzyme thermostability. R. oryzicola population doubled within 12 hr. During this period, 9.26 generations were obtained, with 1 hr and 29 min of interval from one generation to the other, with specific growth rate (µ) of 0.15 (hr). The entire microorganism growth process was monitored during β-1,3-glucanases production, and the maximum value was obtained in the stationary phase in the 48-hr fermentation period. pH and temperature optimum values were 4.7 and 96°C, respectively. The enzyme maintained 88% of its activity when submitted to the temperature of 90°C for an incubation period of 1 hr. The results show that the enzyme can be used in industrial processes that require high temperatures and acidic pH.

Tangerine juice was treated with crude extract containing cellulase from Pseudozyma sp. obtained by liquid fermentation. The thermal stability of cellulase was investigated by incubating crude extract at different temperatures and times. The pulp, obtained from tangerine, was pasteurized at 85 °C for 5 min and then used in a clarification process with a Doehlert experimental design. The results showed that the cellulase obtained from Pseudozyma sp. is thermostable at temperatures of 60, 70 and 90 °C and retained 98%, 88% and 80% of activity, respectively, after a 1-h incubation time. The optimum conditions for clarification were verified by varying the enzyme extract concentration (%, v v -1 ) and the time (minutes) in a shaker at 150 rpm, at 50 °C. The optimum condition for clarification was obtained in the 80th min with a 1.25% enzymatic extract concentration (v v -1 ), resulting in a reduction of tangerine juice viscosity by 65%. The analysis of physical and chemical parameters of tangerine juice after clarification showed that the enzyme extract improved the process responsible for the clarification of tangerine juice. The results are promising since this is a methodology that can be used in the citrus juice industry.

Guava juice is cloudy and viscous, which hinders filtration, decreases yield, and causes the loss of quality after its processing and during storage. This study aimed to evaluate enzymatic treatment effects using crude multi‐enzymatic extracts (CME) obtained from Rhodotorula mucilaginosa, Rhodotorula orizycola, and Pseudozyma sp. produced by submerse fermentation in the extraction of juice guava. Mixtures of 100 ml of guava pulp and multi‐enzymatic extracts proposed by Doehlert planning were incubated under constant agitation at 150 rpm and 50°C, and a Doehlert design was applied as a multivariate optimization strategy. The optimal conditions using the multi‐enzymatic extract were: 0.4% (v/v) of CME for 131 min for the multi‐enzymatic treatment using Pseudozyma sp.; 3.0% (v/v) of CME for 154 min using the R. mucilaginosa CME; and 5.0% (v/v) of CME for 90 min using R. oryzicola. The maximum viscosity reduction values for the juices treated with the CME of yeasts were 10.33%, 86.38%, and 13.33% for the juices treated with the CME of Pseudozyma sp., R. mucilaginosa, and R. orizycola, respectively. The physical–chemical properties were improved after treatment with CMEs, yielding a reduction of clarity, increase of total soluble solids and reducing sugars, and decreasing the acidity (pH) for all treatments with enzymatic extracts of all strains. The yeasts studied showed a potential for CME production to be applied to juice, improving the quality of the juice, and R. mucilaginosa was the most prominent yeast due to most significant reduction of viscosity in guava juice.

Microorganisms that are capable of degrading lignocellulolytic materials can produce extracellular cellulase complexes. Microorganisms are an excellent alternative for the production of cellulolytic complex, since these sources have a high power of multiplication. In this work, we researched the production by the fungus <em>Moniliophthora perniciosa</em>. The production and pH and temperature optimum optimization were studied by Response surface methodology and carboxymethylcellulase (CMCase) characterization. Thermal stability was evaluated at 60, 70, 80 and 90°C. Doehlert experimental design<em> </em>was employed using inductor concentration in five levels (3.0, 4.5, 6.0, 7.5 and 9.0 g L^-1 of yeast extract) and fermentation time was studied in three levels (7, 14 and 21 days). The production of CMC enzyme was higher in the concentration of 7.0 g L^-1 of yeast extract and 19 days fermentation time. CMCase showed optimum pH and temperature at 7.2 and 47°C, respectively. The CMCase retained 88.66% of residual activity after 30 minutes of incubation at 90°C. Due to the characteristic of thermal stability, this enzyme will be studied to be expressed in recombinant microorganisms.